B Putland & R Sciberras

SAG Conference Vancouver, Canada September 22 – 26, 2019


Many ore bodies are getting harder, more abrasive, and lower in grade. One of the issues designers face is minimizing capital and operating costs when treating such ores. Designers often look to secondary or tertiary crushing followed by grinding in a semi-autogenous grinding mill with recycle crusher followed by a ball mill (SABC) or ball mill only circuit when treating extreme ores (Axb<30, BWi >18 and Ai>0.5). This approach is capital intensive and for abrasive ores often results in a circuit with high maintenance and operating costs.

This paper looks at how these extreme ores can also be treated successfully using primary crushing and single stage semi-autogenous or autogenous grinding (S/AG) milling. Benchmarking of this style of circuit is provided with detailed case studies of the design and operation of single stage SAG milling circuit with recycle crushing (SAC) at the Mt. Carlton Au/Cu/Ag and Mako Au projects. Discussed are why these circuits were successful and the challenges encountered.

Lastly, the learnings from these circuits are used to explore the part that autogenous grinding circuits may play in future comminution circuits.


SAG, ramp up, design, commissioning, comminution circuit selection, competent ore, single stage.

Location of full paper


*Brian Putland1 & Rebecca Sciberras1
1Orway Mineral Consultants WA Pty. Ltd. (OMC) Level 4, 1 Adelaide Terrace East Perth, WESTERN AUSTRALIA 6004
(*Corresponding author: This email address is being protected from spambots. You need JavaScript enabled to view it.)


The authors would like to extend sincere gratitude to both Evolution and Toro Gold Limited for having OMC work on the Mt. Carlton and Mako projects. The company would also like to thank the production and maintenance teams on each project for their trust, support, and effort to make these projects successful.

Thanks also go to the engineers involved on each project and their commitment to the concepts discussed in the paper.
Lastly, we would like to thank OMC Ltd. for allowing us to publish the paper.